Master cylinder for hydraulic braking systems



Julyvl9, 1938. w. A. BERTRAND 2,124,363

. MASTER CYLINDER FOR HYDRAULI BRAKING sYsTEMs Filed Feb. V11', 19:57

Patented July 19, 1938 UNITED STATES PATENT oFFicE MASTER CYLINDER FORHYDRAULIC BRAKING SYSTEMS 13 Claims.

This invention relatesto a master cylinder `for a hydraulic brakingsysternand more particularly to a system of this kind designed for usein 'connection with motor driven vehicles, and it is primarily an objectof the invention to provide a master cylinder operating to give a truehydraulic pressure distribution to all brakes and wherein is providedmeanswhereby is locked out suchpart of the system which may becomeineffective without interfering with the operation of the remainder ofthe system.

Another object of the invention is to provide a master cylinder ofthiskind comprising means whereby a part which is locked againstoperation may be conveniently released when desired.

The invention consists in the' details of construction and in thecombination and arrangement of the several parts of my improved master fcylinder for a hydraulic braking `system whereby certain importantadvantages are attained and the device rendered simpler, less expensiveand otherwise more convenientfand advantageous 4for use, as will behereinafter more fully set forth.

The novel features of my invention will here#V inafter be definitelyclaimed.

In order that my invention may be the better understood, I will nowproceed to describe the same with reference to the accompanying drawing,whereinzv Figure 1 is an elevational vView of a diagrammatic characterillustrating a master cylinder or pressure unit constructed inaccordance with i an embodiment of'my invention;

Yturn movement;

Figure 5 is a fragmentary view partly in sec Figure 2 is an enlargedview partly inlongitudinal `section and partly in elevation takenYthrough the block as comprised in Figure 1;

Figure 3 is a transverse sectional view taken substantially on the line3-3 of Figure 2 Vlooking in the direction of the arrow;

Figure 4 isa fragmentary View partly in section and partly in elevationillustrating one of the pistons of a subcylinder locked against retionand partly in elevation illustrating the main piston engaged with asternv of a pistonk for a subcylinder, illustrating the manner hereindis closedvfor releasing a locked piston; and

Figure 6V is a fragmentary view in elevation of the main piston andparticularly illustrating the unlocking sleeve carried bythe mainpiston. As disclosed in the Vaccompanying drawing, B denotes a block ofdesired dimensions which is formed atl one end portion with a maincylinder I which has'in communication therewith a series of subcylinders2 formed in the oppo-` site end portion of the block B. As hereindisclosed, these subcylinders 2 are four in number g but I donot wish tobe understood as limiting myself in this respect as the `number ci thesecylinders may be varied as the requirements of practice may determine.The subcylinders 2 are also preferably equi-distantlyspaced around the.I

axial center of the main cylinder I. Arranged Within the main cylinder Ifor rectilinear movement is the main piston 3 secured to the insertedend portion of the rod 4 which,l

as diametrically indicated in the accompanying y a type to allow forready disconnection `for a purpose to behereinafter moreparticularlyr'referred to. l A

In the present embodiment of my invention, the upper portion of theblock B is formed to drawing, is operatively connected, as at 5, as byT5 provide a reservoir 'I which is in communication '25 at all timeswith the cylinder'I through the ports 8.' This is to takecare of seepageand volume changes of the fluid and also .to allow fluid linto thecylinder I so that there will beV no back pressure when the brakes areapplied.

The subcylinders 2 have leading therefrom t the pipe lines 9 which are'intended Vfor proper' communication with the brake cylinders (not shown)so that upon proper operation of the piston 3 and with the systemnormal, proper pressure istransmitted through the medium of Vthe liquidto effect the setting of the brakes.

It is highly important should for any reason, such as by rupture of aline 9, a part of the system become inoperative to lock out such part'L10 in a manner to permit the remainder cf the .system to operateuntilit is convenient to make the necessary repairs. To accomplishthispurpose the subcylinders 2 have mounted thereinfthe pistons IIi'lxedgto the stems I2. These stems I2 are snugly but freely directedthrough a guide ,plate I4 secured by the screws VI5 or the like to theinner end ofthe cylinder I and partially overlying the inner open endsof the subcylindersA 2.,

The walls of thecylinders `2 at theirginner open ends are formed withthe ports I6 of a length to provide communication between the cylinder Iandthe cylinders 2 when the piston 3 together with the pistons II are infull re-V lease position. This position is preferably maintained by coilsprings I'I positioned within the cylinders 2 for coaction with thepistons II.

' The combined area of the pistons II is less than the area of thepiston 3 so that as pressure movement is imposed by the piston 3 thepistons II must move at'the same speed until the ports I6 are closedwhereupon as the pressure movement of the piston 3 continues the pistonsII must have a greater linear movement to displace Y unit volume of uidthank the corresponding movement of the piston 3. It is, therefore,believed to beV obvious that during this movement the pistons II willmove inwardly `of their cylinders 2 at a greater speed than the pressuremovement of the piston 3 thus assuring a truly hydraulic action upon thelbrakes with which the pipe lines communicate. The stems I2 are of suchlength that when the pistons 3 and II areV in their normally retractedposition the outer extremities of these stems will have direct contactwith the piston 3 so that during the initial setting of the brakes thepistons II will be mechanically operatedby such contact and until theports I6 have-been closed off. lt is also to be stated that'these stemsI2 are of a length to have their outer end portions at all times withinthe cylinder I beyond the guide plate I4.

The outer end portion of each of the stems I2 is, as herein disclosed,bifurcated to provide a kerf I8 which is adapted to receive. a springcatch I9. This catch I9 at one end portion is suitably secured to thebase of the kerf I8 and the remaining portion of the catch normallyprojects laterally beyond the stem I2. The portion 20 of the catchimmediately adjacent to the bottom of the kerf serves as a striker plateto effect movement of the catch I9 entirely within the kerf I8 as suchstein I2 has abnormal movement inwardly of this piston 3 as willhereinafter be more specifically mentioned. As this stem I2 continues onits abnormal inward movement the locking recess 2I of the catch willcome into proper register with the marginal portion of theV guide plateI4 defining the opening 22 in the plate throughl which the stem passes.When this register occurs the inherent resiliency ofthe catch will causethe sameto swing outwardly into locking engagement with suchmarginalportion of the plate I4 whereby said stem I2 is locked againstretraction until the latch is adjusted into released position. The latchI9 outwardly of the recess 2| is provided with an inwardly andYoutwardly inclined portion providing a second striking plate 23. Shouldany one of the lines 9 become ruptured or the iiuid therein leakV outfrom any cause, as the piston 3 starts on its inward l or compressionstroke and the pistons II force or push inwardly beyond the port I5 orbypass as it may be called,- the piston I I within the cylind-er withwhich the ruptured or leaking lineV 9 communicates will have abnormalinward travel bringing the latch I9 into locking engagement with theplate I4. Thus, this particular piston is locked against operation yetno interference or hindrance is offered to the required operation ofthepistons in the other cylinders 2. words, the construction andassembly ofthe master cylinder as herein disclosed isV such that aruptured or otherwise ineffective lineleading to a brake isautomatically cut out and maintained ineffective until after thenecessary repairs or replacements have been made. It is also believed toberapparent that the locked piston I I will close In other the flow ofliquid out from the cylinder I so that the only liquid waste will bethat in advance of the locked piston II.

When it is desired to release the locked piston to allow the same toreturn to its normal functioning position, the operative connectionbetween the rod 4 and the foot pedal E is released as by withdrawal of aclevis pin. 'Ihe piston 3 can then-be readily rotated within thecylinder I by imposing turning movement upon the extended portion of therod 4. The working or presa sure face of the piston 3 has extendingoutwardly therefrom'a sleeve 24 of desired length and of a diameter tosnugly receive the outer or eX- tended portion of any one of the StemsI2. Therefore, after the piston 3 has been rotated within its cylinder Ito bring this sleeve 24 into proper alignment with the locked stem, thepiston'3 isvthen caused to move inwardly of the cylinder I. During thismovement the outer end portion of the locked stem I2 is received Ywithinthe sleeve 24 and the outer end of the sleeve contacts with the strikerplate 23v of the latch causbe obvious that a master cylinder for ahydraulic brake system constructed in accordance with my invention isparticularly well adapted for use by reason of the convenience andfacility with which it may be assembled and operated, and it will alsobe obvious that my invention is susceptible`of some change andmodification without` departing from the principlesand spirit thereofand for this reason I do'not wish to be understood `as limiting myselfto the precise arrangement and V'formation of the several parts hereinshownin carrying out my invention in practice except as hereinafterclaimed.

I claimzy l. A pressure unit for use in a hydraulic braking systemcomprising a main cylindensubcylinders in communication with the maincylinder, each'of said subcylinders being adapted for communication withthe operating mechanism for a brake, a main piston working in the maincylinder, pistons working in the subcylinders, means for connecting themain cylinder with an operator, and stems to which are connected thepistons in the'subcylinders, said stems having free contact with themain cylinder when the main cylinder and subcylinders are in fullrelease, the aggregate working areas of the pistons in thesubcylindersbeing less than the area of the Working face of the mainpiston, said subcylinders having bypasses communicating therewith foralimited distance inwardly from the outer ends of said subcylinders, saidbypasses being also in communication with the main cylinder, the pistonswithin the subcylinders passing beyond said bypasses upon initialunitary movement of the main piston and the pistons within thesubcylinders.

2. A pressure unit for use in ahydraulic braking system-comprising amaincylinder, subcylinders in communication with the main cylinder, each ofsaid subcylinders being adapted for comyfin ziihefsubcylinders,saidstems -having free con-v f5. A.;pressure unitiffcr iu'se 'in ahydraulic vbrak- `Jmu'nic'ationf-with -the :operating mechanism for arfbrake, a :main .piston `working Arin 'the main cylfinder, pistonsworking inthe subcylinders means for .connecting .the' main cylinder*with an 'operaotor, istems f'tofwhichf-are f connected Sthefpistons in`ftheisubcylinders, :said stems Ahaving free 'con- .-lt'act with themain`'cylinder when the rmain, cylinder' and tsubcylinders,are,-rinV fullrelease, the aggregate lwor-king areas .ofthe .pistons in thesubcylindersbeing' less'than'the area of 'thework- .fingface 'of itheymain piston, said Jsubcylinders having bypasses -communicatingvtherewith .for a limited-'distance inwardly :from thefouter ends ofsaid subcylinders, said bypasses being also'in com- .Ihunication'With'the Ima-in cylinder, the .pistons within :the subcylinders passingbeyond 'said by- 4passesupon. initial unitarymovement lof the mainApiston 'andfthe pistons "within 1the subcylinders, :and a vguide .plate:partially overlying the outer mend'oi'eachof :the subcylinde1s,'s'aidoverlying portion fof the :plate .having an :opening 'throughWhichxffreelypassesthe stem of the piston Workping -in said subcylinder.

A pressure unit for use `in faf'h'ydraulic brakxing system ycomprisingamain cylinder, subcyll-inders in communication with the main cylinclen.

'eachi'of .saidsubcylinders being `adapted for cornlmunication .with theoperating mechanism for a brake; a"mainlpiston working in the-maincylin- -d'er, @pistons 'working in 'ithe subcylinders, meansforlco'nne'ctin'g the main cylinder with an `operator, :stems to zwhichvareconnected the vpistons @.tact'with -the mainfcylinder when ythe maincyl- :inder and-subcylindersiare inff-ull release, the aggregate workingareas "of"tl'1e.fpiston's"in `the `subfcylintlers being lless than `the'area of 'the work- 'ing face 'of the main piston, said `subcylindershaving lbypasses con'imunicating therewith lfor a limiteddistanc'e'inwardly from `theouter ends of lsaid fsubcylinders, said bypassesbeing "also in communication with .the main cylinder, 'the pis- .tonszWithin `:the subcylinders rpassing beyond said 4bypasses upon finitialxunitary :movement of `the .main piston andthe pistons Within thesubcylinders, and Imeans .for looking `each of the pis- -tonsa-in `theisubcylinders upon abnormal Amovement lof '-a piston withinfitssubcylinder.

.4. A :pressure "unit for use `in a1 `hydraulic braking systemcomprising a main cylinder, subcyl- -inders-in communication with theVmain cylin- -.der,.each -of :said subcylinders being adapted forcommunicationwith theoperating mechanism for a. brake, a main pistonworking-inthe 'main cylinder., Ypistons Working in the subcylinders,means for connecting Fthe main cylinder with an 4oper- .ator, stems towhich are connected the pistons fin 4the-subcylinders, said -stemshaving f-ree `contact with `the main cylinder When the main cylinder.and .subcylinders are in full release, the aggregate working Yareasofthe pistonsl in the subcylinders Vbeingless than the area of the Workingface of .the ,mainypiston said subcylinders having bypassescommunicatingtherewith forl a .limited distance inwardly from the outerends o said subcylindera said bypasses being also in communication withthe main cylinder, the pistons with'in the subcylinders passing beyondsaid bypasses upon initial unitary movement of the Imain piston and thepistons Within the subcylindem,` means forlocking each of the .pistonsin the subcylinders upon', abnormal movement of a piston within itssubcylinder, and means carried by the main piston for releasing a lockedpiston in .a subcylinder.

fing systemvcoinprisi'ng a main cylinder, subcylin- 'de'rs incommunication with the main cylinder,

each of ffsaid'subcylinders "being adapted for comrriunication withtheoperating mechanism fdr a Y brake, amai'n Jpistonwo'rkin'g in themain cyl- "-inder, pistons working in the subcylinders, means forY'c'or'mectin'gfthe "main cylinder with an operator, sterhs =to'whichare "connected the vpistons in fthe esulocylindera ysaid stems havingfree contact fwth fthe 'main rcylinder when the main cylinder andsubcylindersare'inffull release, the aggregate working 'areas of'thelpistons in the subcylinders -being l'ess 'than "the area of'the-working face of `tliei'nain piston, said subcylinders having `byApasses 'communicating Vtherewith for a limited ldistance `inwardly fromthe router ends of said subcylindera said "bypasses vbeing also incommunication with the `'main cylinder, the pistons within y'thesubcylinders passing beyond said bypasses uponfinitial unitary movementof the main piston and the .pistons within the subcylinders, a guide'plate partially Ioverlying the outer end of each o'fthe subcylinders,said overlying portion Eof the plate having'an opening through whichireely Epasses the 'stem "of Ethe piston Working in said subcylinder,and a locking means vcarried by each'of Jhe stems to engage theguideplate upon undue 'inward 'travel of a piston Within a subcylinder tolock said piston against return movement.

6, -A pressure unit for `use `in arhydraulic brakl ing system comprising-a main cylinder, subcylin- -clers in communication with the maincylinder,

l'eachof 'said subcylinders beingadapted for comnliunicationwith theoperating mechanism for a` brake; a main piston working in the maincylinder, pistons Working in the subcylinders, means forlcon'nectingthe-main 'cylinder with-an opersator, stemsfto which are connected thevpistons in -th'e subcylinders,.said stems :having free c'ontact withthe main cylinder whenV the main cylinder andsubcylinders are in fullrelease, `theaggre- :gate working areas of 'the pistons inthesubcylinders'being less than the area of `the working `face 'of theymalin.pistonfsaid subcylinders having 4bypasses 'communicatingtherewith for a limited distance inwardly from the outer ends of saidsubcylinders, said bypasses being also inl communication wit-nine maincylinder, the pistonswithin the `suliczyli-riders passing beyond said`bypasses upon initial unitary movement'oi the main pistonv and uthepistons within the subcylindrs, a'guide plate partially overlying theI'outer endf'of each of ythe subcylinders, said `overlying portion'of.the plate having an opening through which freely passes'th-e stem'of thepiston working in said subcylinder, A'a locking means 'carried by eachof `the steine to engage the guide plate upon unduejin- -vvaroll travelof a piston within -a subcylinder to rlock said piston against 4returnmovement, and means carried bythe main pistonto engage the locking meansof a locked pistonV to release the same. f

y 7. A .pressure unit for usefin a hydraulic braking system comprisingamain cylinder, subcylinders in communica-tionfwith the main cylinder,each of said subcylinders beingadapted for communication with `the`operating mechanism forY a brake, a main piston working in the ymaincylinder., pistons `working in thesubcylindersjmeans for connecting thelmaincylinderwith anoperator, the aggregate working areas of-thepistons,

:inthe subcylinders being less thansthearea of the working faceofthemainfpistongsaidsubbeyond said bypasses upon initial unitary movement ofthe main piston and the pistons within the subcylinders, said subpistonsbeing free for movement independently of the main piston, each oi said.subpistons having a part for free contact with the main piston when themain piston and the subpiston are in full release.

8. A pressure unit for use in a hydraulic braking system comprising amain cylinder, subcylinders in communication with the main cylinder,each of said subcylinders'being adapted for communication with theoperating mechanism for a brake, a main piston working in the maincylinder, pistons working in the subcylinders, means for connecting themain cylinder with an operator, the aggregate working areas of thepistons in the subcylinders being less than the area of the working faceof the main piston, said subcylinders having bypasses communicatingtherewith for a vlimited distance inwardly from the outer ends of saidsubcylinders, said bypasses being also in communication with the maincylinders, the pistons within the subcylinders passing beyond saidbypasses upon initial unitary movement of. the main piston and thepistons within the subcylinders, said subpistons being free for movementindependently of the main piston, each of said subpistons having a partfor free contact with the main piston when the main piston and thesubpiston are in full release, and means for locking Veach of thesubpistons against return upon abnormal movement of such piston inwardlyof its subcylinder.

9. A pressure unit for use in a hydraulic braking system comprising amain cylinder, subcylinders in communication with the main cylinder,each of. said subcylinders being adapted for communication with theoperating mechanism for a brake, a main piston working in the maincylinder, pistons working in the subcylinders, means for connecting themain cylinder with an operator, the aggregate working areas of thepistons in the subcylinders being less than the area of the working faceof the main piston, said subcylinders having bypasses communicatingtherewith for a limited distance inwardly from the outer ends of saidsubcylinders, said bypasses being also in communication with themain'cylinders, the pistons within the subcylinders passing beyond saidbypasses upon initial unitary movement of the main piston and thepistons within the subcylinders, said subpistons being free for movementindependently of the main piston, means for locking each of thesubpistons against .return upon abnormal movement of such pistoninwardly of its subcylinder, and a member carried by the main piston andextending toward the subcylinders for releasing a locked piston of asubcylinder. Y

10. A pressure unit for use in a hydraulic braking system comprising amain cylinder, subcylinders in communication with the main cylinder,each of said subcylinders being adapted for communication with theoperating mechanism for a brake, a main piston working in the maincylinder, pistons working in the subcylinders, means for connecting theVmain cylinder with an 'operator, the aggregate working areas of thepistons in the subcylinders being less than the area of the working faceof the main piston, said subcylinders having bypassescommunicating'therewith: for a limited Vdistance inwardly from the outerends of said subcylinders, said bypasses being also in communicationwith the main cylinders, the pistons within `the subcylinders passingbeyond-said for locking each of the subpistons against returny uponabnormal movement of such piston inwardly of its subcylinder, and meanscarried by the main piston for releasing a locked piston of asubcylinder;

ll. AA pressure unit for use in a hydraulic braking system comprising amain cylinder, subcylinders in communication with the main cylinder,each of said subcylinders being adapted for communication with theoperating mechanism for a brake, a main piston working in the maincylinder, pistons working in the subcylinders, means for connecting themain cylinder with an operator, stems to which are connected the pistonsin the subcylinders, said stems having free contact with the maincylinder when the main cylinder and subcylinders are in full release,the aggregate working areas of the pistons in the subcylinders beingless than the area of the working face of the main piston, saidsubcylinders having bypasses communicating therewith for a limiteddistance inwardly from the outer ends of said subcylinders, saidbypasses being also in communication with the main cylinder, the pistonsWithin the subcylinders passing beyond said bypasses upon initialunitary movement of the main piston i and the pistons within thesubcylinders, and a spring latch carried by the outer portion of each ofthe stems, the associated subcylinder having a part engaged bysaid latchfor locking the subpiston of the stem in its subcylinder upon abnormalmovement of the piston within its subcylinder.

12. A pressure unit for use in a hydraulic braking system comprising a.main cylinder, subcylinders in communication with the main cylinder,each of said subcylinders being adapted for communication with theoperating mechanism for a brake, a main piston working in the maincylinder, pistons working in the subcylinders, means for connecting themain cylinder with an operator, stems to which are connected the pistonsin the subcylinders, said stems having free contact with the maincylinder when the main cylinder and subcylinders are in full release,the aggregate working areas of the pistons in the subcylinders beingless than the area of the working face of the main piston, saidsubcylinders having bypasses communicating therewith for a limiteddistance inwardly from the outer ends of said subcylinders, saidbypasses being also in communication with the main cylinder, the pistonswithin the subcylinders passing beyond said bypasses upon initialunitary movement of the main piston and the pistons within thesubcylinders, and a spring latch carried by the outer portion of each ofthe-stems, the associated subcylinder having a part engaged by saidlatchfor locking the subpiston of the stem in its subcylinder vupon abnormalmovement of the piston within its subcylinder, the'adjacent portion ofthe stem being cut-out to receive'the latch to permit said latch to bemoved into release position.

13. A pressure unit for use in a hydraulic braking system comprising amain cylinder, subcylinders in communication with theY main cylinder,

each of said subcylinders being adapted for communication with theoperatingV mechanism for a brake, a main piston working in the maincylinder, pistons Working in the subcylinders, means for connecting themain cylinder with an opera-` tor, stems to which are connected thepistons in the subcylinders, said stems having free contact with themain cylinder when the main cylinder and subcylinders are in i fullrelease, the avggregate working areas of the pistons in the subcylindersbeing less than the area of the working face ofthe main piston, saidsubcylinders having bypasses communicating therewith for a limiteddistance inwardly from the outer ends of said subcylinders, saidbypasses being also in communication With the main cylinder, the pisy`tons within the subcylinders passing beyond said bypasses upon initialunitary movement of the main piston and the pistons within thesub-cylin-V cylinder, and a sleeve extending outwardly from the pressureface of the main piston to telescopically receive the outer end portionof a stem upon proper manipulation of the main piston, said sleeve asthe stem enters therein engaging the latch to release the same. f

WALLACE A. BERTRAND.

